On-board diagnostics (“OBD”) is a computer-based system designed to monitor the performance of some of a vehicle engine's major components including those responsible for controlling emissions. The Environmental Protection Agency (“EPA”) requires vehicle manufacturers to install OBD systems for emission control on their light-duty automobiles and trucks beginning with model year 1996. OBD systems (e.g., computer, microcontrollers, and sensors) monitor the vehicle's emission control systems to detect any malfunction or deterioration that causes emissions to exceed EPA-mandated thresholds. One such system, for example, is an oxygen sensor located in a vehicle's exhaust system. The EPA requires that all information monitored or calculated by OBD systems be made available through a standardized, serial 16-pin connector referred to as the OBD-II connector—the standard to which the EPA mandated new cars conform beginning Jan. 1, 1996, is the OBD-II standard. All physical and electrical characteristics of this connector are standard for all vehicles sold in the United States after Jan. 1, 1996. The EPA also mandates that, when emission thresholds are exceeded, a vehicle's OBD system store diagnostic information in the vehicle's central computer so that it can be used during diagnosis and repair.
OBD-II systems monitor a wide range of data that indicate the performance of the host vehicle. For example, this data can be analyzed to determine the vehicle's emission performance. In addition to emissions, other parameters that an OBD-II system monitors include vehicle speed, mileage, engine temperature, and intake manifold pressure. OBD-II systems also query manufacturer-specific data, such as data relating to the vehicle's engine, transmission, brakes, alarm, and entertainment systems. OBD-II systems also make available at the OBD-II connector monitor codes called diagnostic trouble codes (“DTCs”) that indicate a mechanical or electrical problem with the vehicle. DTCs are the codes that typically light a vehicle's ‘service engine soon’ light, or malfunction indicator light (“MIL”).
The OBD-II specification provides for a standardized hardware interface—the 16-pin (2×8) J1962 electrical connector, or the ODB-II connector. The J1962 defines the pin arrangement (“pin outs”) of the connector and leaves some pins unspecified for use at the vehicle original equipment manufacturer's (“OEM”) discretion.
In addition to the OBD-II systems, most vehicles manufactured after 1996 have electronic control units (“ECUs”) that control internal electromechanical actuators. Examples include ECUs that control fuel-injector pulses, spark-plug timing, and anti-lock braking systems. Most ECUs transmit status and diagnostic information over a shared, standardized electronic buss in the vehicle. The buss effectively functions as an on-board computer network with many processors, each of which transmits and receives data. When a vehicle is serviced, data from the standardized buss can be queried using external engine-diagnostic equipment (commonly called scan tools) that connects to the OBD-II connector, which is typically located under the vehicle's dashboard on the driver's side. Data transferred through the connector to the scan tools yields data that identify a status of the vehicle and whether or not a specific component of the vehicle has malfunctioned. This makes the service process more efficient and cost-effective.